Screw and nut actuator



@ph 6 w49. R. G. LE TOURNEAU SCREW AND NUT lACTUATOR Filed Nov. 16, 1944INVENTOR R. GL@ Zburneaw ATTORNEYS Patented Sept. 6, 1949 SCREW AND NUTACTUATOR Robert G. Le Tourneau, Peoria, Ill., assignor to R. G. LeTourneau, Inc., Stockton, Calif., a. corporation of CaliforniaApplication November 16, 1944, Serial No. 563,751

4 Claims.

This invention relates to, and it is an object to provide, an improvedpower driven, screw type actuator adapted to accomplish controlledmotion of relatively movable parts between which the actuator isconnected.

Another object of this invention is to provide an actuator of the typedescribed in which the power loss due to the friction of the screw isrelatively low; this result being obtained by the use of a multiplethread long-lead screw assembly so designed that the circumferentialtravel of the threads upon rotation of the rotation of the screw, isonly approximately twice the corresponding axial movement of said screw.Thus a material advantage is gained over short-lead screws wherein therelatively great movement of the engaged surfaces of the screw assemblyproduces a friction loss out of proportion, practically, to the axialmovement of the screw.

A further object of this invention is to provide a novel drive assemblyfor the actuator screw, said assembly being connected in compactrelationship between said screw and the power source, which is here anelectric motor.

A further object of the invention is to produce a simple and inexpensivedevice, and yet one which will be exceedingly effective for the purposefor which it is designed.

These objects I accomplish by means of such structure and relativearrangement of parts as will fully appear by a perusal of the followingspecification and claims.

The figure of the drawing is a sectional elevation of the actuator.

Referring now more particularly to the characters of reference on thedrawing, the actuator comprises a multiple thread long-lead screw Iwhich projects axially through a cylindrical housing 2, extending withinsaid housing through an elongated hub 3 which includes a tapped bushing3a xed. therein and through which bushing the screw I is threaded. Thebushing 3a is an initially separate part for ease of manufacture and isremovably secured in connection with the hub 3 by means of a radialflange 3b thereon, and cap screws 3c. The hub 3 is rotatably but axiallyimmovably journaled in longitudinally spaced bearings 4 secured in saidhousing. At the rear end of the housing the screw I projects through asealing unit 5.

The forward end of the housing 2 is xed in connection with and opensinto a relatively sha1- low, transversely extending, gear case,indicated generally at 6, the screw projecting through an axial sleeve 1in said case to a termination outwardly thereof. At its forward or outerend the screw I has a clevis 8 non-rotatably xed thereon, said clvisbeing adapted for connection with the part 9 intended to be moved by theactuator, which part 9 is non-rotatable. The actuator is affixed to anon-movable part (not shown) by attaching the housing and case structurethereto. A suitable seal I0 is formed between the inner end portion ofthe sleeve 1 and the adjacent end of the hub bushing 3a. The hub 3 isdriven by a reversible electric motor II by means of a gear train withinthe gear case 6, which gear train comprises the following:

The motor I I is xed to the gear case in spaced parallel relation to thescrew I, with the motor shaft I2 projecting into said case 6. A pinionI3 is xed on motor shaft I2 and meshes in driving relation with arelatively large diameter intermediate gear I4 journaled in case 6, saidgear including a shaft I5 on which a pinion I6 is secured. The pinion I6meshes in turn with a drive gear I1 formed with the hub 3.

It will be seen that upon operation of the motor II, the above describedgear train will function to rotate the hub 3 and to advance or retractthe screw I, depending upon the direction of rotation, and tocorrespondingly advance or retract the movable part 9.

By virtue of the use in the above described actuator of a multiplethread, long-lead screw, I accomplish the relative speed of a cam typeactuator, and also avoid the relatively high friction ,loss of thoseactuators which include a shortlead screw. With the mechanism of myactuator the differential between power input and power output is muchless than with other available mechanisms; this because of the fact thatthe circumferential travel of the threads upon rotation of the screw, isonly approximately twice the corresponding axial movement of said screw.

As shown, the gears and pinions are helically cut in such a manner thatthe thrust on the screw when under load is opposed by the thrust of thegearing. By so doing, considerable thrust load is relieved from thebearings, making for less friction and greater gear eiiiciency.

From the foregoing description it will be readily seen that I haveproduced such a device as substantially fullls the objects of theinvention as set forth herein.

While this specication sets forth in detail the present and preferredconstruction of the device, still in practice such deviations from suchdetail may be resorted to as do not form a departure from the spirit ofthe invention, as dened by the appended claims.

Having thus described my invention, what I claim as new and useful anddesire to secure by Letters Patent is:

1. An actuator comprising a cylindrical housing, a pair of spaced apartbearings mounted in the housing, ,a gear case mounted at one end of thehousingva'ndinopven communication with said housing, a gear disposed inthe gear case, an elongated hub on the gear, such hub projecting intothe housing and being supported .in said bearings, a bushing separatefrom -Jthe hhub but projecting into the latter, meansldetachablgysecuring the bushing immovable relative to the hub, a screw threadedthrough the bushing, a motor xed to the gear case, means connecting themotor in driving rlation withthe gear.

2. An actuator as in claim 1 in which the gear and hub are integral.

3- A11 @tewater-@11191211111 11 111 which the last named metes091111111565 a train, 0f gears disposed in the vcase and connected indriving '4 relation between the motor and the flrst named gear.

4. An actuator as in claim 2 including a protective sleeve surroundingthe screw and extending from the front wall of the case to a pointadjacent the hub, and sealing means between adjacent ends of the sleeveand hub.

ROBERT-G, I iETOURNEAU.

REFERENCES 'CITED The following references are of record in the `ile ofthis patent:

UNITED sTATEs PATENTS

